There has been no reported change of ultrasonographic findings of nucleus pulposus on chemonucleolysis. Wehave found that the particles of herniated nudeus pulposus are highly echogenic and change to low echogenic after chemonucleolysis, On an invitro experimental study, ultrasonography of the surgical specimen of the herniatednucleus pulposus was highly echogenic. After soaking the chymopapain into the surgical specimen of the herniatednuclelus pulposus, the echogenicity was progressively lowered as time passed from 3 minutes to 12 hours. Our preliminary results are divided as two folds: 1. High echogenic shadows of out side of annulus fibrosus onultrasonography of herniated lumbar disc will be important indicator of selection of patients for good therapeuticresults of chemonucleolysis. 2. Progressively lowered echogenicity of high echogenic shadow after chemouncleolysis suggests good reactionn of chymopapain with herniated nucleus pulposus.